Quenching chimney



g- 22, 1967 T. L. BROWNLEY ETAL 3,336,634

QUENCHING CHIMNEY Filed April 22, 1966 3,336,634 QUENCHING CHIMNEY Trenholm Lowell Brownley, Petersburg, Ralph Bennie Stotesberry, Chester, and John William Sublett, Richmond, Va., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Apr. 22, 1966, Ser. No. 544,620 3 Claims. (Cl. 18-8) This is a continuation-in-part of our copending application Ser. No. 322,336, filed Nov. 8, 1963, now abandoned. The invention relates generally to production of synthetic filaments by the melt spinning process and, more particularly, to apparatus for cooling the molten filaments in their advance away from a spinneret.

In the extrusion of molten polymers, to pass freshly extruded filaments directly where they are quenched with a transverse flow of a gaseous cooling medium to condition them for subsequent processing. It is also known to provide increased cooling as the distance from the spinneret increases. However, known techniques and equipment have not proved satisfactory for the quenching of filaments extruded from polymers of higher than normal molecular weight and from various copolymer systems.

It is the object of this invention to provide an improved apparatus for quenching filaments extruded from molten polymer. A corollary objective is the provision of on apparatus particularly adapted for quenching filaments from copolymers and polymers having a very high molecular weight.

The above objects have been accomplished with a chimney construction comprised of successive rectangular, convergently tapered and tubular lengths. The upper rectangular length extends downwardly from and has a top wall apertured for registry with a spinneret assembly. It also has front, side and back walls. Except for provision of openings in the back and front walls for admission of a quenching medium and the outside air, the three chimney lengths are imperforate.

Other objectives and related advantages will be apparent from the following specification wherein reference is made to the accompanying drawing in which:

FIGURE 1 is a perspective view of a preferred chimney embodiment; and

FIG. 2 is a longitudinal sectional view through the chimney of FIG. 1, showing also freshly extruded filaments and a convergence guide.

The chimney construction chosen for purposes of illustration has an initial rectangular length an' intermediate convergently tapered length 12 and a terminal tubular length 14. Length 14 and the adjoining portion of tapered length 12 are streamlined. Initial length 10 is bounded by a back wall 16, a top wall 18, side walls and a front wall which includes hinged door 22. Back Wall 16 has an opening fitted with a diffusion screen 28 through which a quenching medium is discharged from plenum chamber 30. Top wall 18 has an opening adapting it for registry with a spinneret assembly 32 from which emergent filaments advance to a convergence guide 34 (FIG. 2).

Assembly 32 includes an annealing ring 33 which blankets the usual spinneret plate with heated nitrogen or steam and which terminates in registry with top wall 18 of chimney length 10. Except for the fact that ring 33 is it is customary into a chimney United States Patent 0 separate rather than integral, the structure of assembly 32 corresponds generally to that disclosed by Bradshaw in U.S.P. 2,252,689.

In operation, a molten polymer is extruded from spinneret assembly 32 in the form of filaments which advance through ring 33 and the illustrated quenching chimney to convergence guide 34 and thence to a draw winder. A gaseous quenching medium such as air is discharged from plenum chamber 30 through diffusion screen 28 at a relatively low rate (at least 74 cubic ft./ min/ft. of screen) and at a temperature in the range of 1050 C., preferably 10-30 C. However, the size of the screened opening and the quenching medium rate of flow are so related as to produce a flow velocity suificiently high to maintain a relatively stable filament pattern in the chimney. Insuificient flow velocity leads to excessive filament movement and, therefore, to contacts between and fusing of adjacent filaments.

As it exits plenum chamber 30, the quenching flow is directed transversely of the filaments. In view of the relatively low rate of flow, the quenching medium is carried downwardly or cocurrently due to the pumping action of the filaments and a small volume of air is drawn in through the shallow opening above door 22. However, some of the blanket nitrogen and residual monomer in the polymer which is vaporized at the spinneret face as the polymer is extruded are shown off by fitting 36. With annealing ring 33 located as shown, there is a relatively quiescent zone between the spinneret plate and chimney. The cocurrent flow of both the quenching medium introduced through screen 28 and air drawn in through the front wall functions to maintain filament stability in chimney lengths 12, 14 and also to prevent filament fusion. In this connection, length 12 is both tapered and streamlined and length 14 is streamlined to insure non-' turbulent flow therethrough.

With the apparatus disclosed herein, melt extruded filaments are quenched at a relatively slow rate. This is desirable with many copolymers in order to develop the proper crystalline structure for obtaining optimum yarn properties and to permit drawing and winding 'at high speed without difficulty from broken filaments and the like. Likewise, slow quenching processes have been found desirable for homopolymers having very high molecular weights, i.e., polyamides having relative viscosities in the range of 5075 and higher.

Obviously, adaptations and modifications of the illustrated quenching chimney will occur to those skilled in the art without departure from the spirit of our invention which is, therefore, intended to be limited only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In combination with a spinneret assembly and a distant convergence guide, a filament-quenching chimney extending from said assembly toward the guide, said chimney having a top wall apertured for registry with said assembly and being comprised of successive rectangular, convergently tapered and tubular lengths, said rectangular length having front, back and side walls, there being an opening in said back wall extending substantially through its width and downwardly from said top wall, said front wall having a shallow opening adjacent the top wall, said chimney being otherwise imperforate.

2. The chimney of claim 1 wherein is provided a vacuum fitting proximal to and extending across the opening in said front wall.

3. In combination with a convergence guide to which freshly spun filaments advance from a spinneret assembly which includes a dependent annealing ring, a filamentquenching chimney extending from said ring toward the convergence guide, said chimney having successive rectangular, convergently tapered and tubular lengths, said rectangular length having top, front, back and side walls, the top wall being aperture for registry with said ring, the front wall having a shallow opening adjacent said top wall, the back wall having an opening extending substantially through its width and length, said chimney lengths being otherwise imperforate.

References Cited UNITED STATES PATENTS 2,252,689 8/1941 Bradshaw 264-85 2,982,994 5/1961 Fernstrom 264-176 3,067,459 12/1962 Brand 188 3,111,368 11/1963 Romano 188 X WILLIAM J. STEPHENSON, Primary Examiner. 

1. IN COMBINATION WITH A SPINNERT ASSEMBLY AND A DISTANT CONVERGENCE GUIDE, A FILAMENT-QUENCHING CHIMNEY EXTENDING FROM SAID ASSEMBLY TOWARD THE GUIDE, SAID CHIMNEY HAVING A TOP WALL APERTURED FOR REGISTRY WITH SAID ASSEMBLY AND BEING COMPRISED OF SUCCESSIVE RECTANGULAR, CONVERGNETLY TAPERED AND TUB ULAR LENGTHS, SAID RECTANGULAR LENGTH HAVING FRONT, BACK AND SIDE WALLS, THERE 